add the BT_ prefix for all #ifdef guards, to avoid conflicts with developers own header defines.

Fixes Issue 497

//license header
#ifndef BT_RIGIDBODY_H
#define BT_RIGIDBODY_H
class btRigidBody
{
};
#endif //BT_RIGIDBODY_H

src/BulletCollision/NarrowPhaseCollision/btSubSimplexConvexCast.h

@@ -14,8 +14,8 @@ subject to the following restrictions:
 */
 
 
-#ifndef SUBSIMPLEX_CONVEX_CAST_H
-#define SUBSIMPLEX_CONVEX_CAST_H
+#ifndef BT_SUBSIMPLEX_CONVEX_CAST_H
+#define BT_SUBSIMPLEX_CONVEX_CAST_H
 
 #include "btConvexCast.h"
 #include "btSimplexSolverInterface.h"
@@ -47,4 +47,4 @@ public:
 
 };
 
-#endif //SUBSIMPLEX_CONVEX_CAST_H
+#endif //BT_SUBSIMPLEX_CONVEX_CAST_H